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Unmanned Aerial Vehicles (UAV) are being proposed for many applications including surveillance, mapping and atmospheric studies. These applications require a lightweight, low speed, medium to long duration aircraft. Due to the weight, speed, and altitude constraints imposed on such an aircraft, solar array generated electric power can be a viable alternative to air-breathing engines for certain missions. Development of such an aircraft is currently being funded under the Environmental Research Aircraft and Sensor Technology (ERAST) program. NASA Lewis Research Center (LeRC) has built a Solar Electric Airplane to demonstrate UAV technology. This aircraft utilizes high efficiency Applied Solar Energy Corporation (ASEC) GaAs/Ge space solar cells. The cells have been provided by the Air Force through the ManTech Office.

Unmanned Aerial Vehicles (UAV) are being proposed for many applications including surveillance, mapping and atmospheric studies. These applications require a lightweight, low speed, medium to long duration aircraft. Due to the weight, speed, and altitude constraints imposed on such an aircraft, solar array generated electric power can be a viable alternative to air-breathing engines for certain missions. Development, of such an aircraft is currently being funded under the Environmental Research Aircraft and Sensor Technology (ERAST) program. NASA Lewis Research Center (LeRC) has built a Solar Electric Airplane to demonstrate UAV technology. This aircraft utilizes high efficiency Applied Solar Energy Corporation (ASEC) GaAs/Ge space solar cells. The cells have been provided by the Air Force through the ManTech Office.

An experiment was designed, fabricated and tested at the NASA Lewis Research Center to investigate the concept of using the surface layer of the moon to store thermal energy. The concept includes using the energy stored within the surface as a thermal input to drive a solar dynamic power system. The solar dynamic power system would operate using the suns thermal input during the lunar day and would continue to operate during the lunar night using the thermal energy stored within the cavity. The experiment modeled in a lunar thermal energy storage concept by applying a heat flux to the surface of simulated lunar soil equivalent to what a primary and secondary solar concentrator could produce with a concentration ratio of 2000:1. The experiment was designed to determine if the surface layer of the lunar soil could be melted using the equivalent heat flux from a radiative heating element mounted above the simulated lunar soil.

Jet Engines may experience severe vibration due to the sudden imbalance caused by blade failure. This research investigates employment of on board magnetic bearings or piezolectric actuators to cancel these forces in flight. This operation requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the magnetic bearings or piezo electric actuators. This paper will show the architecture of the software system, details of the control algorithm used for the sudden imbalance correction project described above, and the laboratory test results.

Joining of a PdCr Strain Gage with a Hastelloy X carrier shim to Inconel by a rapid infrared processing technique has been investigated at 1150 °C using a nickel based brazing alloy AMS 4777, Ni-7Cr-3Fe-3.2B-4.5Si-.06C in wt%. The effects of the infrared joining parameters on the joint and base material microstructure, joint shear strength, and delamination tendency of the PdCr gage was investigated. Results show that the joint shear strength is as high as 503 MPa when processed at approximately 1150 °C for 120 seconds. Microstructural examinations of the joint with both an optical microscope and a scanning electron microscope indicate that good wetting exists between the brazing alloy with both the Hastelloy X and Inconel 718. And, the Hastelloy X and Inconel 718 exhibits no noticeable change in microstructure due to the rapid processing cycle of the infrared heating process while the stabilized PdCr wire gage shows little change in resistance.

The performance of two 20-kHz actuator power systems being built for an advanced launch system are evaluated for a typical launch scenario using an end-to-end system simulation. Aspects of system performance ranging from the switching of the power electronic devices to the vehicle aerodynamics are represented in the simulation. It is shown that both systems adequately stabilize the vehicle against a wind gust during a launch. However, it is also shown that in both cases there are bus voltage and current fluctuations which make system power quality a concern.

A redundancy strategy for reducing micrometeroid armoring mass is investigated, with application to cryogenic reactant storage for a regenerative fuel cell (RFC) on the lunar surface. In that micrometeoroid environment, the cryogenic fuel must be protected from loss due to tank puncture. The tankage must have a sufficiently high probability of survival over the length of the mission that the probability of system failure due to tank puncture is low compared to the other mission risk factors. Assuming that a single meteoroid penetration can cause a storage tank to lose its contents, two means are available to raise the probability of surviving micrometeoroid attack to the desired level. One can armor the tanks to a thickness sufficient to reduce probability of penetration of any tank to the desired level; or add extra capacity, in the form of spare tanks, that results in survival of a given number out of the ensemble at the desired level.

The NASA Lewis Research Center in Cleveland, Ohio has completed the development and integration of a Power Management and Distribution (PMAD) DC Testbed. This testbed is a reduced scale representation of the end to end, sources to loads, Space Station Freedom Electrical Power System (SSF EPS). This unique facility is being used to demonstrate DC power generation and distribution, power management and control, and system operation techniques considered to be prime candidates for the Space Station Freedom. A key capability of the testbed is its ability to be configured to address system level issues in support of critical SSF program design milestones. Electrical power system control and operation issues like source control, source regulation, system fault protection, end-to-end system stability, health monitoring, resource allocation and resource management are being evaluated in the testbed.

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) has been actively involved in the development of electrical power system test beds to support of the overall design effort. Throughout this time, the SSFP Program has changed the design baseline numerous times, however, the test bed effort has endeavored to track these changes. Beginning in August 1989 with the baselining of an all DC System, a test bed was developed which supported this design baseline. However, about the time of the Test Bed's Completion in December 1990, the SSFP was again going through another design scrub known as Restructure. This paper describes the LeRC PMAD DC Test Bed and highlights the changes that have taken place in the Test Bed configuration and design resulting from the SSFP Restructure Exercise in December 1990.

The National Aeronautics and Space Administration (NASA), Lewis Research Center (LeRC) is responsible for the development, fabrication, and assembly of the electric power system (EPS) for the Space Station Freedom (SSF). The Power Management and Distribution (PMAD) Systems Testbed was assembled to support the design and early evaluation of SSF EPS operating concepts. The PMAD Systems Testbed represents a portion of the SSF EPS, containing intelligent switchgear, power conditioning devices, and the EPS Controllers. The PMAD Systems Testbed facility is discussed, including the power sources and loads available. A description of the PMAD Data System (PDS) is presented. The PDS controls the testbed facility hardware, monitors and records the EPS control data bus and external data. The external data includes testbed voltages and currents along with facility temperatures, pressures, and flow rates. Transient data is collected utilizing digital oscilloscopes.

The SP-100 Space Nuclear Power Program was established in 1983 by DOD, DOE, and NASA as a joint program to develop technology for military and civil applications. Starting in 1986, NASA has funded a technology program to maintain the momentum of promising aerospace technology advancement started during Phase I of SP-100 and to strengthen, in key areas, the chances for successful development and growth capability of space nuclear reactor power systems for a wide range of future space applications. The elements of the CSTI High Capacity Power Project include Systems Analysis, Stirling Power Conversion, Thermoelectric Power Conversion, Thermal Management, Power Management, Systems Diagnostics, Environmental Interactions, and Material/Structural Development. Technology advancement in all elements is required to provide the growth capability, high reliability and 7 to 10 year lifetime demanded for future space nuclear power systems.

NASA is currently involved in the Aircraft Energy Efficiency Program (ACEE) which is directed toward developing technology for more fuel efficient aircraft. As part of this overall program, the Engine Component Improvement (ECI) Project was formulated to address near-term improvements for current engines. One part of this effort is Engine Diagnostics which is directed at investigating the causes for in-service performance deterioration of the CF6 and JT9D high bypass ratio turbofan engines. The other part is Performance Improvement, which is directed at development of component technologies to reduce the fuel consumption of CF6, JT9D and JT8D engines. This paper discusses the Performance Improvement part. Nine of sixteen concepts being developed under the ECI project are now complete and four are in service. The remaining five are being offered to the airlines.